User Datagram Protocol (UDP)

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Whereas TCP is a reliable protocol to ensure that data is transmitted reliably between two devices, the UDP is a connection-less protocol. “Connection-less” here indicates that there is no formal connection creation or closing as is there in the TCP.

Data Packet

First of all, we need to understand what a data packet is. A packet is a unit of data which travels over a network. When you provide data to the computer to be sent over a network, the data cannot be sent all at once. Therefore the data is fragmented or broken down into packets by the concerned protocol and then those packets are transmitted over the network. A packet usually contains the following:

  1. actual data
  2. details of sender
  3. details of receiver
  4. any other options related to the transmission of data

These ingredients except the actual data is bundled together into what is usually called as “header”. Different kinds of packets have different kinds of details in their header and handle data in different ways.


The UDP does not do any error checking of the transmitted packets or does re-transmission of lost or corrupt data packets. It simply sends a packet and forgets about it placing trust on the intermediate devices that they will send the packet to the correct destination. There is no mechanism of acknowledgement in UDP. Thus, data loss may occur in UDP. IT is because of this reason only that UDP is not used in mission-critical tasks or any programs where data integrity is essential.

PORTS: This UDP connection is done between Device A and Device B by using something called “ports” or “internet sockets”. The usability of port can be understood by an analogy to the ports used by ships. When something needs to be sent via ships, the material will need to be sent via ports. Thus a ship starts from a particular port and reaches its destination port. Similarly, when data needs to be sent over a computer network, it is sent via virtual addresses on the device called “ports”. Different protocols use different port numbers. Port number 0-65535 exist on UDP indicating that a device can theoretically accept 65536 UDP connections simultaneously.

For Wikipedia entry on UDP, click here.

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